The present invention relates generally to a process for inhibiting the flow of fracturing fluid through one or more subterranean wells other than the well(s) being hydraulically fractured so as to avoid hydraulic pressure and undesired wellbore fluids, such as gas and oil, in the upper well sections, including casing, tubulars, any artificial lift equipment, and surface equipment, and in one or more embodiments, to such a process wherein the flow of fracturing fluid through such subterranean wells is inhibited by pressuring fluid in the well(s) not being hydraulically fractured to seat a standing valve.
In the production of fluid from a subterranean region, a wellbore is drilled so as to penetrate one or more subterranean zone(s), horizon(s) and/or formation(s) of interest. The wellbore is typically completed by positioning casing which can be made up of tubular joints into the wellbore and securing the casing therein by any suitable means, such as cement positioned between the casing and the walls of the wellbore. Thereafter, the well is usually completed by conveying a perforating gun or other means of penetrating casing adjacent the zone(s), horizon(s) and/or formation(s) of interest and detonating explosive charges so as to perforate both the casing and the adjacent zone(s), horizon(s) and/or formation(s). A perforating gun may contain several shaped explosive charges and are available in a range of sizes and configurations which usually provide for a certain charge density and spacing of the shaped explosive charges both vertically along the wellbore and angularly about the axis of the perforating gun. In this manner, fluid communication is established between the zone(s), horizon(s) and/or formation(s) and the interior of the casing to permit the flow of fluid from the zone(s), horizon(s) and/or formation(s) into the wellbore. Alternatively, the wellbore can be completed as an “open hole”, meaning that casing is installed in the wellbore but terminates above the subterranean region of interest. The well is subsequently equipped with production tubing and conventional, associated equipment, such as sliding sleeves, so as to produce fluid from the zone(s), horizon(s) and/or formation(s) of interest to the surface. The casing and/or tubing can also be used to inject fluid into the wellbore to assist in production of fluid therefrom or into the zone(s), horizon(s) and/or formation(s) to assist in extracting fluid therefrom.
It is often desirable to stimulate the subterranean region of interest to enhance production of fluids, such as hydrocarbons, therefrom by pumping fluid under pressure into the wellbore and the surrounding subterranean region of interest to induce hydraulic fracturing thereof. Thereafter, fluid may be produced from the subterranean region of interest, into the wellbore and through the production tubing and/or casing string to the surface of the earth by means of artificial lifts systems, such as a rod pump, as will be evident to a skilled artisan. Where it is desired to stimulate or fracture the subterranean region of interest at multiple, spaced apart locations along an uncased wellbore penetrating the formation, i.e. along an open hole, isolation means, such as packers, may be actuated in the open hole to isolate each particular location at which injection is to occur from the remaining locations. Thereafter fluid may be pumped under pressure from the surface into the wellbore and the subterranean region adjacent each isolated location so as to hydraulically fracture the same. The subterranean region may be hydraulically fractured simultaneously or sequentially. Conventional systems and associated methodology that are used to stimulate subterranean formation in this manner include swellable packer systems with sliding sleeves, hydraulically set packer systems, ball drop systems, and perforate and plug systems.
Often a liner is positioned and cemented within a substantial portion of an open hole, horizontal wellbore to provide greater well stability and serviceability through the horizontal section of the open hole wellbore. A “plug-and-perf” stimulation technique may be employed in such horizontal wells with cemented liners. In accordance with this technique, a plug for obtaining tubular pressure isolation, including, but not limited to a bridge plug, frac plug, or sand plug, and perforating guns may be positioned within the horizontal section near the toe (end or total depth) of the horizontal wellbore. The plug is then set and the zone is perforated by detonating the perforating gun. The plug and perforating gun are then removed from the wellbore and the fracturing fluids are pumped from the surface and diverted through the perforations into the formation by the set plug. Thereafter, another plug and associated perforating gun is lowered into the horizontal section above the previously treated portion and sequentially activated in a manner as described above. This process is repeated while typically moving from the toe (i.e., the distal end of the wellbore) to the heel (i.e., first point in a horizontal well trajectory where the inclination reaches near 90°) of the wellbore until the desired portion is the horizontal section of the wellbore is entirely stimulated, i.e. fractured.
The advent of drilling horizontal wells and hydraulically fracturing the same to improve recovery from a subterranean region, such as tight shales, has led to certain issues surrounding communication between wells. Prior to that, most wells were drilled in a generally vertical orientation and the spacing between these wells was approved by regulatory agencies and based on an assigned and generally understood drainage area. In many of low-permeability reservoirs, these wells were fractured immediately after drilling, often without any attempt to produce them before fracturing. Vertical wells were deemed spaced a sufficient distance from each other to prevent any unwanted direct fluid communication between wells during the fracturing process. The accepted theory was that vertical fractures created in adjacent wells would be parallel and not intersect each other.
Presently, horizontal wells are routinely drilled and fractured to more efficiently produce fluids from a subterranean region. However, decreased spacing requirements and the generally perpendicular orientation of fractures induced from horizontal wellbores has led to increased communication between horizontal wellbores during and after hydraulic fracturing. Invasion of fracturing fluid into well(s) other than the well(s) being fractured at a given time may result in flooding of offset(s) well and temporary loss of production. Such fluid communication may be a function of distance between wells and the fracture network present in a subterranean region, both naturally occurring and created during the fracturing process. For example, communicating wells often may be up to 3,000 feet apart, while many government agencies regulating drilling may permit horizontal wellbores with spacing as little as 500 feet from each other. Which wells will be subject to invasion of fracturing fluid during fracturing is not always readily evident to a skilled artisan due in large part to a lack of knowledge of the natural and created subterranean fracture network. While offset well communication resulting from fracturing may be temporary, in other instances such communication may be permanent and may cause direct cross-flow between wells, surface spills and damage wellbore integrity which may lead to subterranean contamination. Fluid pressure and undesired wellbore fluids, such as gas and oil, due to offset well communication may also damage well equipment, such as artificial lift equipment and surface equipment.
To inhibit the consequences of communication between offset wells during hydraulic fracturing, operators may pull equipment from the offset wells, such as pumps and rods, run a packer by means of a tubular and set the packer at a subterranean location above the subterranean region being fractured. In this manner, the offset wellbores may be sealed against the invasion of fracturing fluid communicated through the fractured subterranean region and the possible attendant problems associated therewith. However, pulling the existing equipment in a well and running and setting a packer on tubing is expensive, e.g. $300,000, and time consuming. Further, the lost production of hydrocarbons while undergoing such operation is extremely costly and may be extended by complications in setting packer(s). Accordingly, a need exists for a cost effective and efficient process for inhibiting flow of fracturing fluid into offset wells.